Toothbrushes generally comprise a grip handle by which a user may hold the toothbrush and a bristle-carrying head, the head and handle being disposed along a longitudinal head-handle direction. Sometimes the head is replaceably connectable to the handle. Normally there is a neck between the head and the grip handle, being narrower than the adjacent part of the head and handle. The head has a tip end remote from the handle and a base end closest to the handle and the neck is joined to the head at the base end of the head. The junction between the base end of the head and the neck is generally marked by an inflexion point, i.e. a point of sharpest curvature between the head and the neck as seen in plan looking down along the bristles carried by the head, or alternatively by for example the edge of the pattern of bristle tufts closest to the handle.
In toothbrushes, as is well known, the head and grip handle are disposed so define a longitudinal direction (which need not be a straight line) between them, with a width direction perpendicular to this longitudinal direction. Bristles (the term encompasses other dental cleaning elements such as elastomer lamellae or fingers) extend from the head in a bristle direction generally perpendicular to the longitudinal and width directions. The head has a tip end furthest from the handle, and a longitudinally distanced base end closest to the handle and defined by he end of the bristle cluster and/or by an inflexion point in the shape of the head.
It is known to provide the head in the form of plural, particularly two or three, longitudinally elongate sections disposed widthways adjacent across the toothbrush head and being flexibly linked to the handle. A problem associated with known toothbrushes of this type is optimising the bristle distribution to improve cleaning.
For example U.S. Pat. No. 1,323,042 discloses a toothbrush head comprising three flexible sections, the middle section being widened to form a pad adjacent the tip of the head and which extends across the entire width of the toothbrush head adjacent to the tip end, but having a relatively narrow “stalk” linking this pad to the handle. US-D440,404 and US-D436,446 disclose toothbrushes with their heads comprising three sections, each linked to the grip handle by its own respective flexible neck, but each section being narrow relative to length. U.S. Pat. No. 4,864,676 discloses a head in the form of three sections comprising a middle section laterally flanked by two outer sections, the ends of the outer sections remote from the handle forming a partial ring around the end of the middle section, the middle section having bristles only in a small tuft at its end. U.S. Pat. No. 4,472,953 discloses a toothbrush comprising three widthways adjacent flexible necks each having a bristle carrying pad at its extremity remote from the handle, but this results in a head which is disproportionately wide relative to its length.
WO-A01/89344, FR-A-2548528 and U.S. Pat. No. 5,499,421 disclose heads comprising two such sections.
The purpose of such toothbrush heads comprising side by side sections flexibly linked to the handle so as to bend in response to toothbrushing pressures is to improve the ability of the head to adjust to the profile of the teeth, to improve the effectiveness of the head in reaching gaps between the teeth, particularly to achieve this improvement without application of excessive brushing pressures to the teeth, to distribute brushing pressures between the teeth and gums, and to allow a flow of water through the head so that the head may be thoroughly cleaned of for example excess toothpaste, debris etc. after use.